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Humidity control
Choosing either a dessicant dehumidifier (right) or a condensing dehumidifier (bottom right) depends on the application as both products lower humidity levels but do so in different ways
water heat exchanger, which can reduce the cost of this energy consumption.
Due to the need to vent the regeneration airflow
externally, to get rid of the hot wet air coming off the desiccant wheel, desiccant dehumidifiers can also be more complicated to install. A condensing dehumidifier can dry an atmosphere with only an electrical supply and a drain. A desiccant dehumidifier will always need ducting to vent the regeneration airflow away from the area being dried. So with the higher energy costs and the more
complex installation requirements involved in desiccant dehumidification, if a project’s environmental conditions suit a condensing dehumidifier, it will normally be the most cost effective solution. However, temperature isn’t the only determining factor. Condensing dehumidifiers are very effective at maintaining an atmosphere as low as 45-50%RH. If a project calls for a humidity level below this, desiccant technology offers more powerful drying performance. A desiccant dryer can deliver extreme environmental control as low as 1%RH. This is ideal for manufacturing processes, such as lithium battery production, where very low humidity levels are needed. Effectively managing the heat generated during a drying project can also be a determining factor in technology selection. If close environmental control is needed in a project, this nearly always involves both temperature and humidity levels. Although the dehumidifier’s purpose is to control humidity, both technologies will heat the air they dry. This means they have an impact on the temperature management and will need to align alongside any associated heating and cooling equipment. Again desiccant technology offers a more
flexible solution for temperature management, as it is possible to fit pre- or post- modules to a desiccant dehumidifier that can additionally heat or cool the air. There is the possibility with some advanced condensing systems to incorporate remote condensers, which can exhaust the heat air away from the process air delivery. This can provide control over heat management but not to the precise levels offered by desiccant technology. So in summary, for projects that need humidity
control at 45%RH or above and at around 20°C or warmer, condensing dehumidifiers can be the most cost effective solution. Whilst applications that drop below this temperature level, even for short periods of time, or that need less than 45%RH, or advanced temperature management, desiccant dryers offer a much wider performance range.
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July 2021 15
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